docs: def simplex_averaging_matrix(simplices, weight=None, inverse=False):
      '''
      Simplex_averaging_matrix(mtx) is equivalent to simplex_simmation_matrix, except that each row of
        the matrix is subsequently normalized such that all rows sum to 1.
      
      The optional argument inverse=True may be passed to indicate that the inverse averaging matrix
      (of vertices onto simplices) should be returned.
      '''
      m = simplex_summation_matrix(simplices, weight=weight, inverse=inverse)
      rs = np.asarray(m.sum(axis=1), dtype=np.float)[:,0]
      invrs = zinv(rs)
      rng = range(m.shape[0])
      diag = sps.csr_matrix((invrs, (rng, rng)), dtype=np.float)
      return diag.dot(sps.csc_matrix(m, dtype=np.float))